1. Field of the Invention
The present invention relates to a reverse cycle refrigeration system. More specifically, the present invention relates to a combination reversing valve and expansion device to both direct refrigerant flow in a refrigeration circuit and to act as a pressure reducing expansion device depending upon the mode of operation of the refrigeration circuit.
2. Description of the Prior Art
In a conventional reversible refrigeration circuit an indoor heat exchanger and an outdoor heat exchanger are connected to a compressor and an expansion device to form a refrigeration circuit. A reversing valve is incorporated in the system to direct hot gaseous refrigerant to the heat exchanger serving as a condenser and to conduct cooled gaseous refrigerant from the heat exchanger acting as an evaporator back to the compressor.
When a reversible refrigeration circuit is acting to supply heating, the indoor heat exchanger serves as a condenser discharging heat energy from the refrigerant to the indoor air to be conditioned. When the unit is operated in the cooling mode, the reversing valve is switched and the indoor heat exchanger serves as an evaporator receiving liquid refrigerant from the expansion device and absorbing heat energy from the indoor air flowing through the indoor heat exchanger.
The expansion device in a refrigeration circuit serves to allow the pressure of the refrigerant to be reduced. By dropping the pressure from that of the condensing heat exchanger it is possible to evaporate the refrigerant at temperatures such that heat energy may be absorbed from the medium to be cooled. The expansion device is designed to perform a predetermined amount of pressure drop such that the design temperatures are achieved. Depending upon whether the unit is in the heating mode or the cooling mode will effect the sizing of the expansion device. Typically, a lesser pressure drop is desired when the unit is operating in the heating mode than when the unit is operating in a cooling mode.
Refrigerant reversing valves are known in the art and typically include a valve mechanism such that refrigerant flow may be directed from the compressor to either the indoor or outdoor heat exchanger and then conducted back to the compressor as received from either the indoor heat exchanger or the outdoor heat exchanger. Switching the compressor discharge and compressor suction between the heat exchangers is the function of the reversing valve. The reversing valve as disclosed herein utilizes a cylindrical valve gate having passageways therethrough. These passageways are designed to connect the appropriate connections depending upon the position of the valve. Typical expansion devices for use in a heat pump may include capillary tubes selected for each heat exchanger, an expansion device mounted in parallel with the check valve for each heat exchanger such that refrigerant flow in one direction is through the expansion device and in the other direction the refrigerant bypasses the expansion device through the check valve. Likewise, a single device having a movable piston such that the pressure drop in one direction is different from the pressure drop in an opposite direction has been utilized. The present invention utilizes a valve gate having two passageways therethrough, each having its own flow restriction. By switching the valve between one of the two positions, the appropriate expansion of refrigerant is accomplished by regulating the pressure drop.
The present invention additionally concerns the incorporation of the passageways serving as an expansion device in the same valve as the reversing valve such that one valve performs both the functions of the reversing valve and of two separate expansion devices in a reversible refrigeration circuit.